Like other joints and anatomical features of the human body, the distal radioulnar joint is exceedingly complex in its make-up and function. Also like the other joints and anatomical features of the human body, the distal radioulnar joint is unique unto itself and requires specific considerations for its reconstruction or replacement. The complexity and uniqueness of this joint are quite interesting and are, perhaps, best appreciated by considering the skeletal motions which are involved in its movement.
A comparison of FIG. 1A and FIG. 1B in the drawings clearly shows that in the transition of the hand and forearm from pronation (FIG. 1A) to supination (FIG. 1B) the radius and ulna of the forearm transition from a crossed relationship to a side-by-side relationship. Thus, in this movement there is a relative rotation of the radius about the ulna. Also, but much more subtly, during the transition between pronation and supination there is some relative translational movement between the radius and ulna. The consequence of all this is that from a reference point on the ulna, the radius appears to move with a general motion that includes both translation and rotation. Obviously, if this anatomical movement of the distal radioulnar joint is to be duplicated, all of the dynamic components of the movement need to be accounted for and properly coordinated.
The importance of having a workable prosthesis device for the distal radioulnar joint is underscored by the debilitating effects which commonly result when the joint becomes diseased (e.g. arthritis) or destroyed by trauma. It is well known that after excision of the ulnar head, for whatever reason, both forearm bones collide and this is frequently associated with pain, instability or weakness, loss of motion, and loss of sensation on the ulnar side. It is, therefore, of great importance to the patient that these maladies be remedied.
In light of the above it is an object of the present invention to provide a prosthesis for the distal radioulnar joint of a patient which is capable of mimicking the general motion of the anatomical joint that is being replaced. Another object of the present invention is to provide a prosthesis for the distal radioulnar joint of a patient which is sturdy and robust in its operation and longevity. Yet another object of the present invention is to provide a prosthesis for the distal radioulnar joint which has increased range for pronation and supination. Still another object of the present invention is to provide a prosthesis for the distal radioulnar joint of a patient which is relatively easy to manufacture, is simple to use and is comparatively cost effective.